Available online at www.sciencedirect.com Journal of the European Ceramic Society31(2011)847–854Fabrication of wood-like porous silicon carbide ceramics without templates Guangliang Liu a,∗,Peiyun Dai a,Yanzhong Wang b,Jianfeng Yang a,Yabin Zhang ca State Key Laboratory for Mechanical Behavior of Materials,Xi’an Jiaotong University,Xi’an710049,PR Chinab School of Materials Science and Chemical Engineering,Xi’an Technological University,Xi’an710032,PR Chinac Key Laboratory of Hollow Fiber Membrane Material and Membrane Process of Ministry of Education,Tianjin Polytechnic University,Tianjin300160,PR ChinaReceived17September2010;received in revised form15November2010;accepted28November2010AbstractThe porous silicon carbide ceramics with wood-like structure have been fabricated via high temperature recrystallization process by mimicking the formation mechanism of the cellular structure of woods.Silicon carbide decomposes to produce the gas mixture of Si,Si2C and SiC2at high temperature,and silicon gas plays a role of a transport medium for carbon and silicon carbide.The directionalflow of gas mixture in the porous green body induces the surface ablation,rearrangement and recrystallization of silicon carbide grains,which leads to the formation of the aligned columnarfibrous silicon carbide crystals and tubular pores in the axial direction.The orientation degree of silicon carbide crystals and pores in the axial direction strongly depends on the temperature and furnace pressure such as it increases with increasing temperature while it decreases with increasing furnace pressure.©2010Elsevier Ltd.All rights reserved.Keywords:SiC;Porous ceramics;Microstructure;Processing1.IntroductionIn recent years,porous silicon carbide ceramics have attracted particular interest due to their unique properties such as low den-sity,good thermal shock resistance,high mechanical properties and excellent chemical stability at elevated temperature,which make them suitable for a wide range of applications such as catalyst supports,filters for hot gas or molten metal,and high efficiency combustion burners.1–3The performances of porous silicon carbide,especially the mechanical properties are strongly dependent on their pore structures such as their pore size,dis-tribution,interconnection between pores,and pore orientation. Thus,the preferred fabrication method should be able to allow the pore structure of ceramics controlled easily in order to opti-mize their properties.Nowadays,many methods for the fabrication of the porous silicon carbide have been developed,such as polymer replica-tion method,4processes based on the pore forming agents,5,6 and biomorphic porous ceramics produced using natural plant as sacrificial templates.7,8Among these methods,the biomim-∗Corresponding author.Tel.:+862982663453;fax:+862982667942.E-mail address:liuguangliang555@126.com(G.Liu).icking method has recently received intensive attention since the biological structures usually exhibit some unique features of complex hierarchical cellular structures and open porous system.9Up to now,a number of natural plants are used as carbon source such as cellulosefibers(cellulosefiber felts, paper),wood,bamboo,and fruit residues.10–14Among these natural plants templates,wood are widely investigated because the wood-based SiC can retain the anisotropic,hierarchical and elongated tubular structure of wood that has optical proper-ties from the viewpoint of the mechanical properties/density relationship andfluid transport.15–19The special structure and properties of wood are derived from the mechanism of wood formation20–24:water is a transport medium for minerals,gas, sugars,etc.by the short-range diffusion and long distance directional transport due to the gradient of the pressure and concentration formed by transpiration.The temperature affects the change of pressure(transpiration activity);further affect the availability and transport of materials,and the growth of wood. The preferred orientation growth of the anisotropic particles(ray and fusiform initial cells)in a porous(cellular)organization leads to the formation of wood structure.The familiar patterns of woods are known as the annual growth rings andfiber structure.The wood-like SiC should be an ideal candidate for high-temperature exhaustfilters,composites,corrosion-resistant0955-2219/$–see front matter©2010Elsevier Ltd.All rights reserved. doi:10.1016/j.jeurceramsoc.2010.11.036
本文来源：https://www.2haoxitong.net/k/doc/2bda33d384254b35eefd34d3.html
